Cabinet minister Michael Gove has been placed under investigation by Parliament’s standards watchdog.

The probe, opened on Wednesday, relates to the Housing Secretary’s register of financial interests, according to the Standards Commissioner’s website.

It is not known what the investigation relates to.

The details of investigations by the Standards Commissioner, Daniel Greenberg, are kept confidential until the inquiry is concluded and those under investigation are barred from discussing the allegations.

But the Guardian last week reported that Mr Gove failed to register VIP hospitality he enjoyed at a football match with a Conservative donor whose firm he had referred for multimillion-pound personal protective equipment (PPE) contracts during the Covid-19 pandemic.

He was entertained at a Queens Park Rangers match in 2021 with David Meller, whose company Meller Designs was awarded six PPE contracts worth £164 million after the then-Cabinet Office minister passed on its offer of help to officials in 2020, according to the newspaper.

Mr Gove’s spokesperson told the Guardian last week that Mr Gove’s failure to declare the two complimentary tickets he received was an “oversight” and that he had written to parliamentary authorities to inform them of the potential omission.

The spokesperson said: “Mr Gove is grateful to the Guardian for bringing this matter to his attention. He has written to the relevant parliamentary authorities to inform them of a potential omission from the register of members’ financial interests regarding two complimentary tickets he received from Queens Park Rangers Football Club to a match in August 2021.

“Mr Gove routinely declares his attendance at such events in his role as an MP and government minister, as evidenced by other entries in his register of interests and ministerial transparency returns. He apologises for any oversight on his part.”

The MPs’ code of conduct requires them to register gifts, benefits and hospitality over a value of £300.

Mr Gove’s spokesperson declined to comment on the Parliamentary Commissioner for Standards’ inquiry.

The senior Tory is one of six MPs currently being investigated by the Standards Commissioner, all Conservatives.

These include Deputy Speaker Dame Eleanor Laing, Sir Bernard Jenkin and Virginia Crosbie, who are believed to be under investigation for allegedly attending a birthday drinks event in breach of lockdown rules.

The Metropolitan Police closed their investigation into the same allegations in December with no action being taken against any individuals.

Other Conservative MPs under investigation include Bob Stewart and Miriam Cates, who is facing claims that she has caused “significant damage to the reputation of the House as a whole, or of its members generally”.